1. Field of the Invention
The present invention relates to artificial leather sheets of good elastic stretchability. More precisely, the invention relates to artificial leather sheets that do not undergo substantial structure deformation even when repeatedly elongated and deformed. That is, the invention relates to artificial leather sheets that have good elastic stretchability, shape retainability, shape stability and shape recoverability, while having a soft and dense feel. Additionally, an aspect of the present invention relates to napped artificial leather sheets produced by napping at least one face of the artificial leather sheets, while having good uniformity in the napped condition thereof and which have a good feel and have good elastic stretchability and drapability. Furthermore, an additional aspect of the present invention pertains to grained artificial leather sheets produced by forming a coating layer on at least one face of the artificial leather sheets; whereby said grained artificial leather sheets have a good feel and have good elastic stretchability and drapability and in which the coating layer has good surface smoothness and peeling strength even though it is extremely thin. An additional aspect of the present invention also relates to a method for producing those types of artificial leather sheets.
2. Description of the Background
Napped sheets produced by napping at least one face of fibrous textiles such as woven fabrics, knitted fabrics and nonwoven fabrics or at least one face of fibrous substrates having a foamed structure of elastic polymer therein have appearance, texture, feeling and handling that are expressed by the length, density and other properties of raised fibers, which simulate those characteristics of natural suede or nubuck leathers. Therefore, such napped sheets are now mass-produced as napped sheets with suede- or nubuck-finish.
Additionally, napped artificial leathers with suede- or nubuck-finish, which are produced by raising a nap of microfine fibers on the surface of a fibrous structure comprising an entangled nonwoven fabric of microfine fiber bundles and an elastic polymer impregnated thereinto, are known as textile materials being comparable to natural leathers in their structures and having qualities equal to or higher than those of natural leathers. Thus, it is noted that these napped artificial leathers possess excellent properties such as elegant napped surface, soft touch, dense feel, excellent drapability irrespective of its light weight, and unlike woven or knitted fabrics, there is a diminished occurrence of surface unraveling when cut.
There has been a continuous demand for further improving the quality of napped artificial leather sheets to provide high-quality products which are satisfactory in every quality relating to aesthetic sense, feeling, handling, and clothing comfort such as suede appearance, nubuck appearance, soft touch, excellent feel and excellent drapability.
For example, JP-B-01-41742 describes stretchable napped artificial leather sheets with excellent feel, which is prepared from a stretchable entangled nonwoven fabric via a process which entails shrinking an entangled nonwoven fabric comprising elastic polymer fibers (elastic fibers) and inelastic polymer fibers (inelastic fibers) in an areal ratio of 10 to 80%. The proposed artificial leather made of the elastic fibers and inelastic fibers is excellent in drapability. This is, in part, due to the flexibility thereof, which is, in turn, attributable to the elastic fibers all remaining in a free fibrous form therein. However, the proposed artificial leather made of the elastic fibers and inelastic fibers suffers immeasurably during the napping process, for example, by buffing or the like, because of poor binding ability of the inelastic fibers. Consequently, the proposed artificial leather made of the elastic fibers and inelastic fibers, when napped, is rough in appearance, and deviates from the desired suede or nubuck appearance.
JP-B-03-16427 describes artificial leather with good mechanical properties, which is made of multi-component fibers capable of forming two or more kinds of elastic fibers having different melting points and fibers capable of forming microfine inelastic fibers. However, this artificial leather is problematic in that its low-melting elastic fiber constituents provide only a small binder effect, which results in an artificial leather that is unable of attaining an excellent suede-look.
JP-B-05-65627 describes artificial leather with good appearance, which is produced by impregnating polyurethane into a nonwoven fabric made only of sea-island fibers capable of forming inelastic microfine fibers, removing the sea component by solvent extraction to form the inelastic microfine fibers, and then dyeing. However, since the nonwoven fabric does not include elastic fibers, the artificial leather loses its original structure after repeated extensional deformations. Additionally, the artificial leather is not soft to the touch, is rough feeling, and has poor drapability, which is, in part, due to the fact that polyurethane resin impregnated into the nonwoven fabric forms a foamed sheet structure.
JP-B-01-41742 and JP-B-03-16427 describe methods that produce stretchable artificial leathers, but do not produce artificial leathers capable of having a napped surface of raised fibers with good appearance. Alternatively, the method described in JP-B-05-65627 provides for artificial leather that has good appearance, but experiences poor stretchability, feel, and drapability.
Accordingly, it is an object of the present invention to overcome the shortcomings of the previously described products and procedures, in order to provide an artificial leather sheet, whose elastic stretchability, feel, and drapability characteristics are excellent; a method of making the same; and a napped artificial leather sheet and a grained artificial leather sheet that are excellent in appearance.
As a result of extensive studies to attain the object as above the inventors have found the method mentioned below and have reached the present invention.